In the past, many devices have been proposed as attachments for trucks to assist the operator in loading or unloading cargo from the bed or body of the truck. For example, lift gates are often used to raise heavy or bulky objects up to the level of a truck bed so that the objects may be easily moved into the bed of the truck.
Such lift gates usually comprise a platform which is pivotally secured to a hydraulic mechanism and pivoted upwardly to a vertical position when not in use, so that the platform is pivoted through an arc of about 90.degree. to a horizontal position, and the hydraulic system is actuated to lower the platform to the ground. Then, the cargo is loaded onto the platform, and actuation of the hydraulic system raises the platform, while maintaining a horizontal attitude, until it is substantially the same height as the bed of the truck, at which time the cargo is moved into the bed of the truck.
Another type of loading attachment for a truck utilizes an inverted U-shaped boom, the legs of which are attached to the bed of a pickup truck. The cross-bar of the boom carries a winch which is used to lift a load. In the stored position, the crossbar of the boom is positioned immediately behind the cab of the truck, but when pivoted, the crossbar is extended rearwardly beyond the rear of the truck. A load may be engaged by a cable on the winch, and lifted by the winch. Then, by pivoting the crossbar toward the front of the truck, the load is moved forwardly over the bed of the truck, and then lowered into the bed.
This latter type of loading mechanism is shown in U.S. Pat. Nos. 4,383,791 to Louis J. King and 4,265,585 to Wallace H. Hawkins. Both of these devices are inteded for attachment to a pickup truck, the King device being secured to the rear of the bed, and the Hawkins device being secured to the top of the sides of the bed.
Another similar device is shown in U.S. Pat. No. 2,750,056 to R. A. Dow, this device being used with a dump body truck.
One of the difficulties associated with these prior devices has been that they are not as rugged as often required for use with large or heavy loads. Since the U-shaped boom must of necessity be open between the side legs to enable the load to "pass through" the boom, there cannot be any diagonal bracing as might otherwise be used to strengthen the boom. Thus, all forces are transmitted to the pivot points of attachment.
Hawkins attempts to strengthen his device by securing the legs to channel members which in turn are secured to the top of the side rails of the bed, and King attempts to provide a secure mounting by using heavy bolsters mounted in the bed of the truck. However, the nature of the Hawkins device is such that when not in use, the boom is elevated slightly above the cab of the truck such that it would often be in the way, and the mounting arrangement of King significantly reduces the width of the bed available for use.
Thus, these prior devices, while being advances in the art, still possess some disadvantages which hamper their common use.
Accordingly, a primary object of this invention is to provide a self-loading attachment for a truck which overcomes the disadvantages of the prior art devices.
Another object of this invention is to provide a self-loading attachment for a truck which is ruggedly secured to the frame of the vehicle.
A further object of this invention is to provide a self-loading dump-body truck which does not interfere with the normal operation of the dump body.
Yet another object of the invention is to provide a self-loading attachment for a truck which is ruggedly secured to the frame of the vehicle.
Still another object of the invention is to provide a self-loading attachment for a dump truck in which common hydraulic cylinders are used for operating both the loading attachment and for operating the dump bed.
Yet a further object of the invention is to provide a self-loading attachment for a dump truck which is capable of simple, one-man operation.
Still a further object of this invention is to provide a self-loading dump truck having a loading boom operated by the same hydraulic cylinders as the dumping bed, with a novel release mechanism enabling separate or combined operation.